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Frank, Normally you
motor towards the surface and blow MBTs at or near the surface that way you get
many more MBT blows (~6x the number you would get blowing at 150 fsw).
Also, why not carry your ballast blow air on the outside of the hull to
increase internal space? You are going
to have a lot of difficulty getting out of a normal sized PSUB in an emergency
with a regular sized scuba tank. From practical experience, a typical
pony bottle (16 cf) will not be very useful for escape from 150 fsw…a 40
cf bottle will get you to the surface safely (approximately the same diameter
as a 16 cf bottle but longer). As to a
scrubber, you want to use oxygen and not air for emergencies. If you use
air, your cabin pressure will constantly rise due to nitrogen buildup while
oxygen should keep your cabin pressure approximately constant if correctly used
(CO2 scrubbed equals O2 added). How do you
conveniently get a CO2 tank refilled when you need to make a lot of
dives on a long weekend? The CO2 system will be more expensive
to build as compared to air, CO2 with moisture forms carbonic acid
so your corrosion rate goes up, and maintenance costs increase due to having to
maintain scuba and CO2 regulators. The gain is not worth the
pain. Please remember the KISS principle around PSUBs. R/Jay Respectfully, Jay K. Jeffries Andros Is., It is the mark of an educated mind to be able to
entertain a thought without accepting it. From: Hi Jay. Both good points. My thought was
that the volume per cubic foot of available tank space for air versus CO2 might
help in a small sub when the tanks are inside and taking up valuable space. A standard scuba tank at 80 cubic feet of
air takes up quite a bit of space. Now, let me ramble for a minute. 2 people on board, diving at 150 feet,
want to blow ballast dry maybe 3 times each dive. ( one to come up, one to
try but fail to come up, and one more to come up after you fix whatever it
was that failed.) Hopefully you get it right by then.But if it still won't come
up........ Now you need two tanks for escape air,
and enough air with a scrubber to stay stuck for three days while you hope
someone can get to you. That makes about 6 scuba tanks. What if you could replace all the
ballast blow with one liquid tank, ( 3 blows, or 3 scuba tanks.) With a small sub, it's getting real
crowded in there with all those tanks. I don't think anyone carries that much air
in a small sub, but more is better than less! Just wondering.Frank D.
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